Scuba Science 3 - Coral Reefs in a Rapidly Changing World

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Scuba Science 3 - Coral Reefs in a Rapidly Changing World

Richard B. Aronson* and Ian G. Macintyre^ *Florida Institute of Technology ^Smithsonian National Museum of Natural History Scuba-based observations on coral reefs in the 1960s conveyed the impression that reefs were in excellent condition and subject to rare natural disturbances. Beginning in the 1970s, however, hurricanes, infectious diseases and coral bleaching fostered a non-equilibrial view of reef systems. Accelerating degradation in recent decades, driven primarily by human activities, has transformed our vision of coral-reef ecology from non-equilibrial to downright apocalyptic. We can predict the decadal- to centennial-scale future of reefs by placing their current state within the context of their Holocene history. Such a paleoecological analysis turns on two questions. First, can we detect the current state of degradation in the Holocene record of the reefs? And second, have these sorts of episodes occurred in the past? We have used a portable, diver-based technique to extract push-cores from reef frameworks in the Caribbean and the tropical eastern Pacific. Identification and radiocarbon dating of the constituents have enabled us to reconstruct the Holocene histories of the reef systems. In the lagoon of the Belizean barrier reef, Discovery Bay, Jamaica, and a coastal lagoon in Caribbean Panam?, the composition of coral assemblages was static for millennia until it changed radically in recent decades. The current state was detectable in the cores and had not occurred before. In Belize and Jamaica the cause was the regional outbreak of an emergent coral disease. In Caribbean Panam? turnover was caused by declining water quality, driven by changing patterns of land use. Recent mass coral mortality from the 1982--1983 El Ni?o event was not recorded in cores from the eastern Pacific; however, the cores displayed a millennial-scale hiatus in vertical reef growth, apparently tied to past climate change. The current hiatus in reef accretion will lead to reef drowning unless local protections are combined with global actions to mitigate climate change. Recorded on 05/24/2010 at 9:25 a.m. ET

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